UST check pointer/de-reference order

I stumbled across some code where pointers are de-referenced and then
checked for NULL.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/liblttng-ust-ctl/ustctl.c b/liblttng-ust-ctl/ustctl.c
index 9789413f2a4ce8c1b3737e4a43157a2a1aa68b8b..80aed04aede83b8d79894989357c514aae1126d3 100644 (file)
--- a/liblttng-ust-ctl/ustctl.c
+++ b/liblttng-ust-ctl/ustctl.c
@@ -732,7 +732,7 @@ void ustctl_unmap_channel(struct lttng_ust_shm_handle *handle)
 struct lttng_ust_lib_ring_buffer *ustctl_open_stream_read(struct lttng_ust_shm_handle *handle,
        int cpu)
 {
-       struct channel *chan = handle->shadow_chan;
+       struct channel *chan;
        int *shm_fd, *wait_fd;
        uint64_t *memory_map_size;
        struct lttng_ust_lib_ring_buffer *buf;
@@ -741,6 +741,7 @@ struct lttng_ust_lib_ring_buffer *ustctl_open_stream_read(struct lttng_ust_shm_h
        if (!handle)
                return NULL;
 
+       chan = handle->shadow_chan;
        buf = channel_get_ring_buffer(&chan->backend.config,
                chan, cpu, handle, &shm_fd, &wait_fd, &memory_map_size);
        if (!buf)
@@ -784,11 +785,12 @@ int ustctl_get_mmap_len(struct lttng_ust_shm_handle *handle,
                unsigned long *len)
 {
        unsigned long mmap_buf_len;
-       struct channel *chan = handle->shadow_chan;
+       struct channel *chan;
 
        if (!handle || !buf || !len)
                return -EINVAL;
 
+       chan = handle->shadow_chan;
        if (chan->backend.config.output != RING_BUFFER_MMAP)
                return -EINVAL;
        mmap_buf_len = chan->backend.buf_size;
@@ -805,11 +807,12 @@ int ustctl_get_max_subbuf_size(struct lttng_ust_shm_handle *handle,
                struct lttng_ust_lib_ring_buffer *buf,
                unsigned long *len)
 {
-       struct channel *chan = handle->shadow_chan;
+       struct channel *chan;
 
        if (!handle || !buf || !len)
                return -EINVAL;
 
+       chan = handle->shadow_chan;
        *len = chan->backend.subbuf_size;
        return 0;
 }
@@ -823,12 +826,13 @@ int ustctl_get_max_subbuf_size(struct lttng_ust_shm_handle *handle,
 int ustctl_get_mmap_read_offset(struct lttng_ust_shm_handle *handle,
                struct lttng_ust_lib_ring_buffer *buf, unsigned long *off)
 {
-       struct channel *chan = handle->shadow_chan;
+       struct channel *chan;
        unsigned long sb_bindex;
 
        if (!handle || !buf || !off)
                return -EINVAL;
 
+       chan = handle->shadow_chan;
        if (chan->backend.config.output != RING_BUFFER_MMAP)
                return -EINVAL;
        sb_bindex = subbuffer_id_get_index(&chan->backend.config,
@@ -841,11 +845,12 @@ int ustctl_get_mmap_read_offset(struct lttng_ust_shm_handle *handle,
 int ustctl_get_subbuf_size(struct lttng_ust_shm_handle *handle,
                struct lttng_ust_lib_ring_buffer *buf, unsigned long *len)
 {
-       struct channel *chan = handle->shadow_chan;
+       struct channel *chan;
 
        if (!handle || !buf || !len)
                return -EINVAL;
 
+       chan = handle->shadow_chan;
        *len = lib_ring_buffer_get_read_data_size(&chan->backend.config, buf,
                handle);
        return 0;
@@ -855,11 +860,12 @@ int ustctl_get_subbuf_size(struct lttng_ust_shm_handle *handle,
 int ustctl_get_padded_subbuf_size(struct lttng_ust_shm_handle *handle,
                struct lttng_ust_lib_ring_buffer *buf, unsigned long *len)
 {
-       struct channel *chan = handle->shadow_chan;
+       struct channel *chan;
 
        if (!handle || !buf || !len)
                return -EINVAL;
 
+       chan = handle->shadow_chan;
        *len = lib_ring_buffer_get_read_data_size(&chan->backend.config, buf,
                handle);
        *len = PAGE_ALIGN(*len);